<!DOCTYPE html>
<html lang="en">
	<head>
		<meta charset="UTF-8" />
		<meta http-equiv="X-UA-Compatible" content="IE=edge" />
		<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no" />
		<title>Title</title>
	</head>
	<body>
		<button id="btn1">按钮1</button>
		<button id="btn2">按钮2</button>
		<button onclick="demo()">按钮3</button>
		<script type="text/javascript">
			const btn1 = document.getElementById("btn1");
			btn1.addEventListener("click", () => {
				alert("按钮1被点击了");
			});

			const btn2 = document.getElementById("btn2");
			btn2.onclick = () => {
				alert("按钮2被点击了");
			};

			function demo() {
				alert("按钮3被点击了");
			}
		</script>
	</body>
</html>
